Heart failure continues to increase at epidemic proportions in the United States. Heart failure is characterized by a number of abnormalities at the cellular level in the various steps of excitation-contraction coupling. One of the key abnormalities in both human and experimental heart failure is a defect in sarcoplasmic reticulum (SR) function, which in turn is responsible for abnormal intracellular calcium handling. Deficient SR Ca2+ uptake during relaxation has been identified in failing hearts from both humans and animal models and has been associated with a decrease in the expression and activity of SR Ca2+-ATPase (SERCA2a). In rodent models of heart failure, our laboratory has validated the concept that increasing the expression of SERCA2a does indeed restore contractility and normalize intracellular calcium cycling. In addition, the importance of the SR calcium handling has been based on results showing that enhancing SERCA2a activity by ablating its endogenous inhibitor, phospholamban, using antisense strategies or by phosphorylating phospholamban by constitutively activating the inhibitor of phosphatase (1-1) improves function of failing cardiomyocytes. To further extend these results that have clinical promise for the treatment of congestive heart failure, we will test the following hypotheses: 1) that enhancing calcium cycling by either increasing SERCA2a, ablating phospholamban, or increasing the level of a constitutively active form of I-1 will improve hemodynamic parameters in a porcine model of cardiomyopathy;2) that the long-term overexpression of SERCA2a, ablation of phospholamban, or overexpression of the constitutively active form PP1-I will improve survival and induce beneficial ventricular remodeling. To test these hypotheses, we will take advantage of new vectors that have been developed for gene transfer, namely adeno-associated virus for long term expression and the development of new techniques of gene transfer in porcine models that can be readily applicable to humans. Understanding the role of calcium regulation in cardiomyocyte dysfunction and developing approaches to local modulation of these pathways through somatic gene transfer, may provide novel therapeutic approaches for the management of heart failure.